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An hybrid acoustic-oceanographic method for estimating the spatial distribution of sound.

P. Felisberto and S.M. Jesus and
SiPLAB-FCT, Universidade do Algarve
8005-139 Faro, Portugal

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Ref.: Proc. European Conference on Underwater Acoustics, ECUA'2006, (ISBN:), p., Carvoeiro,Portugal, June 2006.

Abstract : Several ocean phenomena, like internal waves or upwelling, give rise to spatial disturbances of the temperature/sound speed. The classical methods to found the spatial distribution of these disturbances is based on in-situ measurements with CTD, XBT, thermistor chains, etc. These direct methods are generally costly in terms of time and resources. More recently, methods for remote sensing temperature disturbances in the ocean by acoustic means, known as acoustic tomography were introduced. Acoustic tomography is interesting specially if simple low cost acoustic systems could be used. This work, starting from such an acoustic system, proposes a method for estimating the distribution of temperature/sound speed disturbances in the ocean and its uncertainty. The proposed method is based on a two step procedure. Firstly, a matched field technique is used to estimate the "mean" sound speed disturbances between sound sources and receivers. In the second step, a spatial distribution of the sound speed disturbances is found using a ray tracing method. The method also allows to include in-situ measurements in the estimation, reducing the uncertainty. The applicability of the method is demonstrated by simulations based on real data from the INTIMATE'98 sea trials.

ACKNOWLEDGMENT: this work was partially supported by FCT project ATOMS -POCTI/P/MAR/15296/1999.